A device of the type is known from DE 198 40 760 A1 (corresponding to U.S. Pat. No. 6,112,745). Such devices are used in conjunction with so-called CPAP respirators (Continuous Positive Airway Pressure), with which a constant airway pressure, which assists the spontaneous breathing, is set for the patient, e.g., in connection with the treatment of sleep apnea.
The prior-art device comprises an outer part and an inner part, which are rotatable in relation to one another and are fitted together by means of a snap-in connection. The external diameter of the inner part and the internal diameter of the outer part are selected to be such that an annular gap is formed, through which the breathing gas can flow off into the environment from the inner area. The two free ends of the prior-art device are connected to a breathing mask, on the one hand, and to a flexible breathing tube, on the other hand, and the torsional moments possibly developing at the flexible breathing tube can be extensively eliminated due to the rotatability of the outer part in relation to the inner part.
The diameters of the outer part and of the inner part, which form the annular gap, must be exactly coordinated with one another in order for a sufficiently high pressure to be able to be built up in the flexible breathing tube, on the one hand, and for flow noises due to the breathing gas flowing out of the annular gap to be reduced to a minimum, on the other hand. The width of the annular gap changes due to manufacturing tolerances, and it is also not possible to prevent the inner part from being in contact with the outer part on one side, as a result of which an asymmetrical annular gap becomes established, which has an adverse effect on the pressure conditions and the flow noises.